Upgrade maven-source-plugin 3.3.1 -> 3.4.0 (#2010)

See:
- https://github.com/apache/maven-source-plugin/releases/tag/maven-source-plugin-3.4.0
- apache/maven-source-plugin@maven-source-plugin-3.3.1...maven-source-plugin-3.4.0

Author: Picnic-DevPla-Bot

pom.xml

@@ -1344,7 +1344,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-source-plugin</artifactId>
-                    <version>3.3.1</version>
+                    <version>3.4.0</version>
                     <executions>
                         <execution>
                             <id>generate-source-jar</id>